x86: enable CONFIG_MMC_SDHCI_ACPI for x86_64

x86: enable CONFIG_MMC_SDHCI_ACPI for x86_64

Some x86_64 single board computer (including Atomic Pi)
has onboard emmc, but requires CONFIG_MMC_SDHCI_ACPI driver
to use or boot from it.

Here is boot message for the mmc device

[    2.838008] mmc0: SDHCI controller on ACPI [80860F14:00] using ADMA
[    2.857536] mmc1: SDHCI controller on ACPI [80860F14:01] using ADMA
[    2.950019] mmc0: new HS200 MMC card at address 0001
[    3.158271] mmcblk0: mmc0:0001 M52516 14.6 GiB
[    3.170290] mmcblk0boot0: mmc0:0001 M52516 partition 1 4.00 MiB
[    3.177191] mmcblk0boot1: mmc0:0001 M52516 partition 2 4.00 MiB
[    3.183963] mmcblk0rpmb: mmc0:0001 M52516 partition 3 4.00 MiB, \
chardev (248:0)

Other lines changed in this config file are introduced by menuconfig.

Signed-off-by: Mengyang Li <mayli.he@gmail.com>